NCOA4-Mediated Ferritinophagy in Iron-Dependent Brain Development

摘要：发育中的神经元对铁的需求很高，以支持其新陈代谢、生长和 差异化。然而，游离铁会产生氧化应激，并具有细胞毒性。以避免神经损伤 缺铁(ID)和过载、神经元铁水平必须严格调控。铁蛋白复合体的作用 通过存储不立即使用的铁来调节细胞内铁的可获得性。在时间段内 对于高铁需求(例如，发育)，必须控制铁蛋白铁的释放，以防止ID.Ferritin噬菌体， 铁从铁蛋白中释放出来并输送到铁需求较高的部位(如线粒体)的过程。 最近以发展红细胞(RBC)为特征。核受体辅活化子4(NCOA4)是 通过选择性地将铁蛋白定向到溶酶体来启动铁蛋白铁动员的特定货物受体 自噬。吞铁蛋白对维持线粒体血红素合成所需的铁的供应至关重要 在发展RBCs方面。目前还没有关于NCOA4或吞铁蛋白在神经元中的作用的数据 发展，导致我们对储存在铁蛋白中的铁是如何释放的理解上的巨大差距 在这一高度铁敏感的过程中受到调控。神经元性吞铁蛋白的失调可能导致严重的 铁负荷不足或超负荷，具有显著的临床后果。这项提案关注的是早产儿ID，因为 它在世界各地普遍存在，并永久性地损害神经行为功能(例如，学习和 记忆)在儿童中。ID在发育中的海马神经元中占有相当大的比例 学习/记忆缺陷。在这个神经元亚型中发现的铁蛋白铁调节的基本原理将 可能适用于所有快速发育的神经元。我们假设，类似于RBC中的铁处理 在发育过程中，通过NCOA4介导的铁噬菌体释放的铁形成了一个铁池，这是必不可少的 对于正常的神经元发育和功能。Aim 1使用我们独特的慢性早期生命体外模型 海马神经元ID测试NCOA4和铁蛋白吞噬是否是最佳神经元所必需的 通过调节铁的可获得性来发展。我们假设NCOA4的丢失将扰乱神经元铁 动态平衡并损害关键的神经发育过程(即线粒体呼吸、神经元树突 和突触的形成)。目的2将目的1‘S的体外结果翻译到活体脑中以揭示 NCOA4和吞铁蛋白在调节海马神经元铁中的发育年龄依赖性作用 利用率。我们假设，NCOA4介导的铁噬菌体提供了一种铁的来源，这是在 出生后，当神经元的铁供应受到限制时，从储存铁转向利用铁(即ID)。我们会 使用两个独特的海马区特异性转基因小鼠系来测试这一点，这两个系建立了神经元铁破坏的模型 吸收(Slc11a2KO)或储存(Ncoa4KO)。拟议中的研究结果将改变目前的范式 神经元铁稳态是如何在发育过程中被控制的，开启了丰富的新研究 有可能为常见的铁相关脑部疾病提供新的治疗策略。

ABSTRACT: Developing neurons have high iron requirements to support their metabolism, growth, and differentiation. Yet, free iron can produce oxidative stress and be cytotoxic. To avoid neurological damage from iron deficiency (ID) and overload, neuronal iron levels must be tightly regulated. Ferritin protein complexes play a critical role in regulating intracellular iron availability by storing iron that is not immediately used. During times of high iron demand (e.g., development), ferritin iron release must be controlled to prevent ID. Ferritinophagy, the process by which iron is released from ferritin and delivered to sites of high iron demand (e.g., mitochondria), was recently characterized in developing red blood cells (RBCs). Nuclear receptor coactivator 4 (NCOA4) is the specific cargo receptor that initiates mobilization of ferritin iron by directing ferritin to lysosomes via selective autophagy. Ferritinophagy is critical for maintaining the supply of iron required for mitochondrial heme synthesis in developing RBCs. There are currently no data on the role of NCOA4 or ferritinophagy during neuron development, causing a significant gap in our understanding of how the release of iron stored in ferritin is regulated during this highly iron-sensitive process. Dysregulation of neuronal ferritinophagy could result in severe iron underload or overload with significant clinical ramifications. This proposal focuses on early-life ID because it is prevalent throughout the world and permanently impairs neurobehavioral function (e.g., learning and memory) in children. ID specifically within the developing hippocampal neuron accounts for a significant portion of the learning/memory deficits. Basic principles of ferritin iron regulation discovered in this neuronal subtype will likely apply to all rapidly developing neurons. We hypothesize that, similar to iron handling during RBC development, iron released through NCOA4-mediated ferritinophagy forms an iron pool that is that is essential for normal neuron development and function. Aim 1 uses our unique in vitro model of chronic early-life hippocampal neuronal ID to test whether NCOA4 and ferritinophagy are required for optimal neuronal development by regulating iron availability. We hypothesize that loss of NCOA4 will disrupt neuronal iron homeostasis and impair critical neurodevelopmental processes (i.e., mitochondrial respiration, neuronal dendrite and synapse formation). Aim 2 translates Aim 1’s in vitro findings to the in vivo brain to reveal the developmental age-dependent role of NCOA4 and ferritinophagy in regulating hippocampal neuron iron utilization. We hypothesize that NCOA4-mediated ferritinophagy provides a source of iron that is required during the postnatal switch from iron storage to utilization and when neuronal iron supply is restricted (i.e., ID). We will test this using two unique hippocampal-specific transgenic mouse lines that model disruptions to neuronal iron uptake (Slc11a2 KO) or storage (Ncoa4 KO). Findings from the proposed studies will shift the current paradigm of how neuronal iron homeostasis is controlled during development, opening up a wealth of new research avenues with the potential to inform new therapeutic strategies for common iron-related brain disorders.